Review The figure is a cross section through three long wires with linear mass density 57.0 g/m. They each carry Part A equal currents in the directions shown. The lower two wires are 4.0 cm apart and are attached to a table. ( Figure 1) What current I will allow the upper wire to "float" so as to form an equilateral triangle with the lower wires? Figure Express your answer with the appropriate units.